Pipes made of polyethylene have become popular in transporting water or gas, for instance in houses and in municipal water distribution. Polyethylenes having a high or medium density are frequently used in such pipes due to their good mechanical properties and ability to withstand pressure. Especially pipes made of multimodal polyethylene having a density of from about 947 to 953 kg/m3 have become increasingly popular. Such pipes and polymer compositions suitable for making them are disclosed, among others, in WO-A-00/01765, WO-A-00/22040, EP-A-739937, EP-A-1141118, EP-A-1041113, EP-A-1330490, EP-A-1328580 and EP-A-1425344. A co-pending European Patent Application No. 06020872.5 discloses flexible pressure-resistant pipes made of bimodal polyethylene and having a density of from 940 to 947 kg/m3.
Such pipes, however, suffer from the disadvantage that the pipes made of HDPE materials are not flexible enough so that they could be wound to a coil which is preferred in certain applications. Flexible pipes have been made from linear low density polyethylene and they are disclosed, among others, in EP-A-1574549. A co-pending European Patent Application No. 06024952.1 discloses flexible pipes in PE63 category having a density below 940 kg/m3. However, such pipes often lack the sufficient mechanical properties that are required from pipes used for transporting water or gas at high pressure. Especially such pipes do not qualify for PE80 or PE100 category.